The gene-enzyme system alpha-glycerolphosphate dehydrogenase in Drosophila melanogaster represents a model system for the analysis of epigenetic processes which control or modulate development. The working hypothesis in this loaboratory is that each isozyme is the product of the same structural gene and that the differentiation of each form represents a developmentally significant post-translational event. Utilizing this system, we are asking the following questions: (1) Waht kind of a structural modification is occurring that differentiates a single polypeptide into multiple molecular forms and leads to a functional divergence of each? (2) In what manner is the modification process regulated to give rise to developmentally distinct and tissue specific isozymes from a single structural gene? (3) Since the isozymes presumably differ only in a post-translational modification of the primary sequence, what effect does this modification have on the stability of each molecular form in terms of intracellular turnover? (4) Since the structural gene product is tissue and developmentally distinct in expression, what classes of regulatory genes can be identified and what is their mode of action? (5) Can a distinction be made between rates of synthesis and degradation in mutants that affect the accumulation of alpha-GPDH molecules? The function of such regulatory genes and their organization in the eukaryotic genome is the principal goal of this research project.